Speed sensors can be implemented into vehicle transmissions to measure the relative speed of rotatable transmission components. Contemporary sensor options include laser sensors responsive to fluctuations in reflective light and those responsive to magnetic flux. Since most transmissions use non-transparent lubricants like oil between moving components, sensors detecting magnetic flux are generally preferred over laser sensors. The detected change in magnetic intensity (ΔH) due to the presence of a transmission component is dependent upon its distance away from the sensor.
The measured speed of certain transmission components can be used to govern clutch timing to improve on the accuracy of shift point and shift feel and to control the speed of a continuously slipping system such as a torque converter clutch. However, these sensors can add axial length to the transmission when used to measure the speed of a buried or inwardly nested transmission component.